Treatment of hydrocarbon oils



June 22, 1937. w. F. HOUGHTON TREATMENT OF HYDROCARBON OILS Filed May25, 1933 fill/enfor Patented June 22, 1937 2,084,342- TREATMENT ornrnaocannon oms Willard F. Houghton, Swarthmore, Pa., assignor to TheAtlantic Refining Company, Philadelphia, Pa., a corporation ofPennsylvania Application May'25, 1933, Serial No. 672,786

@2 Claims. (01.196-13) The present invention relates to a process andapparatus for obtaining continuous countercurrent contact between two atleast partially immiscible liquids, and particularly to the extraction 5of components Irom mineral oils with a solvent which will selectivelydissolve such components. This invention is particularlyapplicable tothe solvent extraction of mineral oils containing considerablequantities of normally solidhydrocar- 11011 compounds or waxes, as wellas being, adapted to the extraction ofnon-wax-bearing oils. y

In carrying out my process, the two fluids, viz.,

the selective solvent and the mineral oil to be I extracted, are broughttogether in countercurrent l5 flow and intimately mixed. The mixture isthen allowed to settle, and the separated products,

'1. e., the undissolved oil and the extract, are con- I tinuouslywithdrawn from the system.

It has been found that the best results are ob m tained when a pluralityof units are provided for mixing the fluids and thereafter separatingthem, in combination with means for efiecting the flow oi fluids incouhtercurrent relation from one unit toanother, and at the same timecontrolling the 5 flow with a minimum amount of regulation. For

example, alternate mixing and settling chambers may be provided as asingle structure, said structure being suitably partitioned to form acompact series of extraction stages, or the structure may comprise aseries of individual mixingand settling chambers suitably spaced onefrom another and connected by means adapted to maintain countercurrentflow.

Apparatus of the preferred construction comprises a tank divided bypartitions into a series of alternate mixing and settling chambersadapted to permit the 011 being extracted to flow therethrough. Themixing tanks discharge into their respective settling tanks by gravityflow thru an orifice," while the settling tanks discharge into theirnext adjacent mixing tanks by gravity flow across weirs. The liquid'level in the settling chamber is governed by the height of the overflowweir at the point of discharge into the succeeding mixing tank. Byproviding common double walls between the various tanks, the equipmentis rendered extremely compact and the heat radiating'surface of theapparatus is decreased so that a minimum amount of insulation isnecesequipment. Means are provided to regulate the withdrawal of liquidfrom the bottom of eachj of the settling tanks at a predetermined rate,

and to maintain the interface between the un- 55 dissolved, oil and thesolvent at a desired level .of liquid than actually overflows,v itscomplete sary to maintain the desired temperature in the 7 within Thelevel of theintertace between the two'liquld layers is regulated byproviding at the bottom of thesettling tank, a drawofi-con- 1 sisting ofa substantially verticalgpipe, from the upper endof which the solvent isdischarged. By regulating the height of the discharge and of the pipe,the level of the interface betweenrthetwo liquids is controlled sincethe interface level rises or falls until equilibrium is established, andthen remains constant until otherjchanges are made in the height of thedischarge'pipe, or-changes occur in the'compositi'on of the liquidmixture.

The regulation of the height ot the discharge 1 pipe may be accomplishedin various ways,- such as a swing joint which permits-moving it to or Pfrom the vertical position; a flexible end. which may bebent togive thedesired level; or preferably, it may discharge into, an overflow vesselthru the bottom of'which thelpipe extends by means of a liquid-tightslip joint which'permits vertical motion of the vessel, so that liquiddischarging from the pipe fills the vessel and overflows into a secondvessel from, which it is conducted by a pump to the succeeding mixingtank or other point of disposal. 'The height of the overflow vessel andthe interface level may be varied by moving the former vertically on thedrawf ofi pip'e,1e. g., by supporting-it from an operating spindlewhichpasses thru a-threaded yolk and is provided with an adjustingwheel. "with 30 this arrangement, the pump cannot remove liquid 1 ata'taster rate than desired, and bysettingthe pump to withdraw a somewhatgreater quantity removal is assured so that theregulation necese v saryis reduced to the minimum. The apparatus has the advantage that theoperation maybe easily regulated since the newer liquidbelng-ex tractedis entirely by gravity and since the system of regulating thewithdrawaiot solvent prevents its removal at a faster rate'thanthat-atwhich it is supplied, and insures itscirculation at a predeterminedrate. 1

In placexof a single ta k divided into compartments by means ofpaitlons, a plurality of tanks may be set up in-serles, with a-layerof-in-* sulating :material between adjacent walls of adjoining tanks topermit maintenance ofdifierenttemperatures in the several tanka when separate tanks'are employed, itis-preferred that the overflow weir of thesettling chamber discharge onto a chute leading to the next mixing tank;pipes are usually undesirable forconducting liquid. from the settlingtanks; since in certain types of oil, the content of wax is sufliv cientto form a curdy mass which flows .andseparating tanks are employed, theliquid mixture issuing from the mixing tanks may be g I For purposes ofillustration, reference is made to the accompanying drawing in which;

. drical construction,- and conveyed to the respective settling tanksbymeans oipumps, in'place oi the gravity flow described j herein, by wayof illustration.

Fig 1 shows a top view 01 a preferred arrange ment of'my extractionsystem; f V Fig. 2 represents a side view 01 the same; and Fig. 3 shows,in simplest 'form,

;In' Fig. 2 there is showna double walled closed tank, partitioned oil.into alternate settling tanks (I, 2, ands), and mixing tanks (4, 5,-and8). The settling tanks are of rectilinear construction,

:and are in step-likejarrangement; the intermediate mixing tanks areofdouble walled cylincentrallylocated upon the settlingtank partitions.The settling tanks areprovided wlthoverflow weirs (9, ,andll),

and interface-level" regulators andsolvent draw- -oils (l1, 2d, and 25),while the mixing tan'ksare equipped with'paddle stirrers (1)" or othersuitable mixing devices, discharge orifices (8, l0, and i2) and'solve'ntsupplypipesils, 23,and 28). A system of low pressure'pump's-and feedpipes is 2 so arranged-as to maintain aregulated counterseparationofsolvent from plied from the bottom of settler mixer 4 thru orifice nc,pipe 23.;

current flow thru the extraction stages. s

In the operation of my proce'ssjI may choose, for examplanitrobenzeneasthe selective solvent anda wax-containing mineraloil'as the stock tobe selectivelyextracted. The oll stock sup- "a. storage tank (not shown)flows thru pipe21, pump 28, pipe 29, and chilling device lliinto-the.topof mixing tank. The selective solvent, i. e., nitrobenzene, isconducted from a supply tank(notshown) thru jplpe .llheat exchanger. l5,pump I8 and pipe is into the top or mixing tank 6. After sufllcient oiland solvent hasbeen suppliedto the system, a continuous countercurrentflow will be set up, and the extraction process will'fcommence tolunction. The oil stock charged to-mixing tank I, togetherwith thepartially used solvent ii-om zyflowing' thru regulator 20, pipe, pump26, and pipe 30 into feed pipe 29', thru chilling device 34, pipe"28'and into the. top of mixing tank- 4, said oil and solvent arethoroughly contacted by the stirrer 1, and" the mixture flowsbyxgravity, fromthe bottom of 8 into settling chamber I. In chamber ,l,aseparation of undissolved oil and. solventcontainingdissolved oil iseffected by the .diflerence in gravity, the undissolved 011 comprisingthe upper layer andnthe solvent the The spent solvent, having passedthru regulator 25,plpe ll, 33 into storage, prior to the dissolved oil,as by vacuum distillation. The undissolved oil fraction containingsubstantially all the wax and-a pump I2, and pipe small quantity ofsolvent, occupies the. upper portion oi'settleril,

and flows by gravity, over theiwelrlinto ,the ucceeding mixing tank 5,

' intdwhich is simultaneously delivered relatively freshrsolvent fromthe bottom 01' settler-l, thru. regulator", pipe 2!, pump 22,-heatexchanger .Theoil and solvent are herein regulator 20, pipe 24,

v tacting process is again effected in c 6', the mixtureflowing thruorifice l2 into settler a sectionalfend' view of myinterface levelregulator and settler.

shown) in the respective ing and settling chambers,

settling tank '2 contains a the solvent which is thru the orifice ill atthe bottom of the mixer, into settler 2 where the separation ofundissolved oil and solvent layers iseflected. The solvent i fromthebottom oi settler 2 is withdrawn thru ",into mixing tank 6 where.iresh solvent is introduced from storage supplythru pipe, I, heatexchanger I5,.pump II and pipe I.

3, the separation "of layers isaccomplishedzby pump 2 andplpe 2. intooil \feed pipei 29,- and thereafter thru chilling device 34,. intomixing tank I to'eirect'iurther I The conmixingtankq 15.

settling, and the solvent is continuously with. I

drawn from the bottom oi'the settler un-. dissolved oil and wax now overthe weir l3 and are removed thru pipe I 'toqstoragc prior to therecovery of the solvent or other treatmentiflln the eventthat the oilstock belngpxtracted tains relatively large quantities arrangement oimechanical scrapers, (not shown) may be constructed in the upperiend.otthesetsame surface scrapin apparatus may be satisiactorilyused.

Under certain conditions,

tdmainta'inthe variousmixing. and settling c p of wax, of, the a, "orderor 30% or- 40% or the volume. 0!. oil. an

it as. desirable. 1

tanks at difl'erent temperatures. .This' maybej eifected by installingheating orcooling coils (not!) ,In' thecase'oi the single,partitionedchamber type ofconstruc y g partitions separating, the stagesailords sumcientfinsulatlon to prevent tion, the double walled seriousradiation losses. The type of extraction apparatus comprising aseries'oi' individual mixing and settling tanks maylikewise' be provideda with suitable insulation and means for heating or coolingiasdescribedfabove. With either type a of construction, the system can,with slight motile v flcations, handle very volatilejsolventad. ,e., at

pressures substantially above f atmospheric.

Fig. 3 shows a 'sectionalendjvlew oi" the mixand more particularly thedetails of the interface, 7 mixture oi'gsolvent and oil which wasintroduced from the precede in mixing tank thru an orifice correspondingto orifice -10 (see Fig. 2) near the center'oIQthe tank wall. Thesolvent and c 7 W v ers separate by diil'erence in gravity, the formersettling to the bottom, and*the latter manna the upper portion "ofthechamber. The solved oil layer, upon reachinga liquidlevel ll, flowsby gravity, over the weir ii-into. the succeeding mixing tank' 6" iscontinuously discharged thru orifice l2" into the next settling tank. 1

For purposes oi illustration, the interface level ment 31' from which itwhere iurther with more solvent is' eflected by means or stirrer 1, andthis mixture oil flows :thru thepipe 30 ,1' and spills-overth'e upperedge l or collecting compart-f is withdrawn by pump 7 levelregulator.The

undissolved oil laythe depth of the-settling:

thru pipe 45. The vessel 38 functions as an adjustable extension of pipe36, a liquid-tight slip joint being made at 43 which permitsof raisingor lowering the vessel 38, which is suspended by strap 39, threaded rod42 and adjusting wheel ll. The rod 42 passes yolk 40 at the topofcollecting compartment 31. In operation, the pump which withdraws thesolvent from the bottom of collecting compartment 31 thru pipe 45, isoperated at a somewhat greater capacity than is necessary in order toinsure complete removal of the overflow from collecting compartment 30.The construction of vessel 31 is such that any siphoning action isprevented, inasmuch as the liquid level in 31 is never allowed to reachthe upper edge of .vessel a.

The regulation of the position of the interface level with regard to thesettling tank is effected by changingthe height of the U-tube drawoif.

A relatively small change in height of the drawoff tube will cause agreat difference in the position of the interface level, due to thedifference in specific gravity between the solvent and the undissolvedoil. For example, assuming the gravity of the solvent to be 1.2, and theundissolved oil 0.9 whenthe head of liquid in the settling tank ismaintained constant ata total depth of 11.66 ft., and the verticallength of the drawofl tube at .10 ft., I find that the interface levelis5 ft. from the bottom of the tank. If the drawoff tube is lowered from10 ft. to' a height of 0.5 ft., the interface level 9.5 ft., ashortening of is found to be 3.0 ft. from tankbottom, and if the tube isshortened from 10 ft to'9 ft.-the interface is found to be Witha'constant total head and gravities as given, a change of 0.1 ft.in-raisingor lowering the drawofl tube will cause the interface level torise or fall 0.4 ft. j

The particular advantage of this device is the ability -to maintainsired height in the settling tank, regardless of the change incompositionof the mixture of oil and solvent entering the settler, bymerely adjusting the height of the drawofl. tube. At the same time thisregulator controls the quantity of liquid available for the pumpstowithdraw from the settler and reduces pump and flow regulation to aminimum. This type of drawofi eliminates the necessity of the floatcontrol for pump regulation, said float control being particularlyundesirable when operating where there is a liquid interface.

It will be appreciated by those skilled in the art, that my inventionaflords several marked advantages over extraction processes of the priorart, particularly (1)-gravity flow of undissolved oil, 1. e.,wax-bearing oil, from the'settler to the succeeding mixer, therebyavoiding the necessity for special pumps to handle very waxy oils; (2)-replacing of pipes by weirs or chutes to direct or convey theundissolved oil from the settler into the succeeding mixer; (3)-meansfor regulating the rate of withdrawal of solvent from the bottom of thesettler, and the control of the position of the interface level by asimple regulator thus reducing the adjustment of pumps to a minimum,float controls for pumping; (4)-compactness of the multi-stageextraction system as herein described, and its ability to handle verywaxy stocks as readily as wax-free stocks.

thru and is supported by versal viscosity at fraction comprising 1.0ftxfrom tank bottom.

- of 560 F., fire test of 660- F.,, and a the interface level at any de-I current extraction of a vided with stirring means to the mid-sectionof the succeeding settling r 65 provided, in the upper part, with anoverflow weir as well as. eliminating undesirable.

While 1 have reference to a three-stage continuous countercurrentsystem,

stages. Furthermore, the ratio of solvent to oil any particularInumberof stages. My invention A comprehends a system comprising one or more:

stock and the temperatures of contacting, and

settling will be governed entirely by the character of the oil to betreated,

ing example: I

A Barber's Hi1 distillate having a Saybolt Uni- 210 F. of Y304. seconds,an A. P. I. gravity at F., fire test of 670 F., and pour test of 50F.-",

was treated in a five stage continuous counter-.

current extraction apparatus with 183% of nitrobenzene. settlingchambers were as F., 2nd stage 79-F., 3rd stage follows: 1st stage'68"F., 4th stage The temperatures maintained in the" the solvent employedin the treatment, and the duality of theproduct desired. p My processmay be illustrated by the follow- F.,and ,5th stage 113 F} The upperlayer-of oil from the 5th stage'settler and the lower layer ofnitrobenzene and oil dissolved therein from the bottom of the 1st stagesettler were each distilled under vacuum to remove the solvent. The

oil functions recovered had the followingproperties: The undissolved oilfraction comprising.

39.9% of the stock had a Saybolt universal viscosity at 210 F., of 136seconds, an AP. 1. gravity at 60? F., of 26.42 flash of 570 F.,firetestof 650 F., and pour test of 60 F. The dissolved oil 60.1% ofthe. stock had a Saybolt universal viscosity at 210 F., of 754 seconds,an A. P. I. gravity at 60 F., of 12.1", flash divided into a pluralityof alternate mixing and" settling compartments I step-like arrangement,at r by partitions, .said compartments being in least one of the mixingcompartments being propour .test I vided with stirring means and anorifice outlet to the mid-section of i the succeeding. settlingcompartment, each settling compartment having the lower part thereofcompartment, each settling compartment being mixing compartments beingproand an orifice outlet.

7 5o an overflow weir in the upper part and'means for withdrawn toa'preced-.

to the succeeding mixing compartment, and in J the lower part with anadjustable level drawoif provided with a receiverin non-siphoning relaitionship to said drawoif, means for withdrawing liquid from saidreceiver and passing said liquid into apreceding mixing compartment.WILLARD F. HOUGH'I'ON.

